Disk alignment apparatus and method for patterned media production

ABSTRACT

A method for aligning a disk with an imprinting surface is described. In one embodiment, the method includes passively aligning an imprinting surface with the disk and imprinting the disk with the imprinting surface. A first air-bearing mandrel freely guides a first centerline of the disk into coincident alignment with a second centerline of the imprinting surface.

CROSS-REFERENCE To RELATED APPLICATION

This application is a divisional of application Ser. No. 10/243,380,filed Sep. 12, 2002, hereby incorporated by reference.

FIELD OF THE INVENTION

This invention relates to the field of disk drives, and morespecifically, aligning and imprinting of disks for use in disk drivesystems.

BACKGROUND

A disk drive system typically consists of one or more magnetic recordingdisks and control mechanisms for storing data within approximatelycircular tracks on a disk. A disk is composed of a substrate and one ormore layers deposited on the substrate. In most systems, an aluminumsubstrate is used. However, alternative substrate materials such asglass have various performance benefits such that it may be desirable touse a glass substrate.

To produce a disk substrate from a blank sheet of metal-based materialsuch as aluminum or aluminum magnesium, the sheet may be stamped togenerate a disk substrate having an inner diameter (ID) and an outerdiameter (OD). After stamping the ID and OD, the disk-shaped substratemay be heat treated to remove stresses and then polished. The disk maythen be coated with a polymer overcoat.

The trend in the design of magnetic hard disk drives is to increase therecording density of a disk drive system. Recording density is a measureof the amount of data that may be stored in a given area of disk. Onemethod for increasing recording densities is to pattern the surface ofthe disk to form discrete tracks, referred to as discrete trackrecording (DTR). DTR disks typically have a series of concentric raisedzones (a.k.a., lands, elevations, etc.) storing data and recessed zones(a.k.a., troughs, valleys, grooves, etc.) that may store servoinformation. The recessed zones separate the raised zones to inhibit orprevent the unintended storage of data in the raised zones.

One method of producing DTR magnetic recoding disks is through the useof a pre-embossed rigid forming tool (a.k.a., stamper, embosser, etc.).An inverse of the surface pattern is generated on the stamper, which isdirectly imprinted on the surface(s) of a disk substrate. Thin filmmagnetic recording layers are then sputtered over the patterned surfaceof the substrate to produce the DTR media having a continuous magneticlayer extending over both the raised zones and the recessed zones. Toimprint tracks on a data storage disk substrate, an imprinting templatemay be attached to a flexible support, whose curvature can be altered byapplying hydrostatic pressure. By suitably varying the pressure, theimprinting surface can be brought into contact with the disk substrate.

An imprinted disk may not be viable if the imprinting surface is notconcentrically aligned with the disk substrate. Imprinted tracks thathave excessive offset from a centerline of the disk substrate may notoperate properly when read by a disk drive head. This requirement isparticularly important in disks used in hard disk drives in which tracksmay need to be imprinted on both sides. As such, imprinting a diskrequires an alignment step, in which a centerline of the disk is alignedwith a centerline of the imprinting surface, before the disk substrateis actually imprinted.

Current alignment methods typically require the use of high precisionactuators or robotics. For example, the high precision actuators wouldfirst determine a centerline for the disk substrate and align it with acenterline of the imprinting surface. The use of such high precisionactuators and robotics are expensive, with high maintenance costs,inconsistent accuracy and reliability, and slow cycle times. The highprecision actuators and robotics are also significant pieces ofmachinery, requiring large amounts of floor space.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and notlimitation, in the figures of the accompanying drawings in which:

FIG. 1 illustrates one embodiment of a semi-passive disk alignmentapparatus for patterned media production.

FIG. 2 illustrates one embodiment of a passive disk alignment apparatusfor patterned media production.

FIG. 3 illustrates another embodiment of a semi-passive disk alignmentapparatus for patterned media production.

FIG. 4 illustrates another embodiment of a semi-passive disk alignmentapparatus for patterned media production.

FIG. 5 illustrates, in flowchart form, one method for aligning a diskfor patterned media production.

FIG. 6 illustrates, in flowchart form, an alternative method foraligning a disk for patterned media production.

FIG. 7A illustrates a cross-sectional view of one embodiment ofimprinting surfaces sealed over die portions.

FIG. 7B illustrates a cross-sectional view of another embodiment ofimprinting surfaces sealed over die portions.

FIG. 8 illustrates one embodiment of a thermodynamic press that may beused for imprinting a disk substrate.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forthsuch as examples of specific, components, processes, etc. in order toprovide a thorough understanding of various embodiment of the presentinvention. It will be apparent, however, to one skilled in the art thatthese specific details need not be employed to practice variousembodiments of the present invention. In other instances, well knowncomponents or methods have not been described in detail in order toavoid unnecessarily obscuring various embodiments of the presentinvention.

It should be noted that the apparatus and methods discussed herein maybe used with various types of disks. In one embodiment, for example, theapparatus and methods discusses herein may be used with a magneticrecording disk. Alternatively, the apparatus and methods discussedherein may be used with other types of digital recording disks, forexample, a compact disk (CD), a digital video disk (DVD), and amagneto-optical disk.

In one embodiment, the apparatus and method described herein may beimplemented with an aluminum substrate. It should be noted that thedescription of the apparatus and method in relation to aluminumsubstrates is only for illustrative purposes and is not meant to belimited only to the alignment and imprinting aluminum or metal-basedsubstrates. In an alternative embodiment, other substrate materialsincluding glass substrates may be used, for example, a silica containingglass such as borosilicate glass and aluminosilicate glass. Othersubstrate materials including polymers and ceramics may also be used.

An apparatus and methods for using the apparatus to align a disk forpatterned media production are described herein. In one embodiment, thedisk is passively aligned with an imprinting surface, therebyeliminating the need for high precision actuators and alignment tools.In another embodiment, the apparatus includes a very high-precision dieset that establishes the inherent side-to-side alignment andrepeatability of the patterned media. An air-bearing supported alignmentmandrel resides in the top die, as well as an imprinting surface coupledto a circular elastomer pad that accommodates thickness variations of adisk substrate. A centerline for the air-bearing mandrel matches acenterline for the imprinting surface. The bottom die contains anannular air “manifold” located substantially near the ID of a cavity toconstrain the disk before alignment. All of the die body elements andmandrel are of circular configuration and like materials, thusminimizing thermal distortion and maintaining critical clearances atair-bearing surfaces. The alignment process is passive because theair-bearing mandrel freely guides a centerline of the disk intoalignment with a centerline of the imprinting surface.

In an alternative embodiment, a precision die set establishes afundamental side-to-side alignment and repeatability of the patternedmedia. Air-bearings are used in multiple places to attain precise, totalsystem alignment. Specifically, air-bearing supported alignment mandrelsare disposed in the top and bottom die portions. The air-bearingalignment mandrels have intermeshing, tapered nose portions. The bottomdie rests in a double air-bearing nest with one planar surface and onespherical surface. A circular elastomer pad to accommodate substratethickness variations may also be disposed central to the air-bearingmandrels adjacent to the substrate. Most of the die body elements andmandrel are of circular configuration and like materials, thusminimizing thermal distortion and maintaining critical clearances atair-bearing surfaces.

In another embodiment, an air-bearing supported alignment mandrelresides in the bottom die. Hermetically sealed die foils are welded overshallow cavities on top and bottom die pieces. Most of the die bodyelements and mandrel are of circular configuration and like materials,thus minimizing thermal distortion and maintaining critical clearancesat air-bearing surfaces.

In another alternative embodiment, the patterned foils are aligned viapico-actuators and held in place. An air-bearing supported alignmentmandrel resides in the bottom die to receive the disk. Most of the diebody elements and mandrel are of circular configuration and likematerials, thus minimizing thermal distortion and maintaining criticalclearances at air-bearing surfaces.

Referring to FIG. 1, a cross-sectional view of one embodiment of a diskalignment apparatus 100 for patterned media production is shown. In oneembodiment, the apparatus 100 passively aligns and imprints a disk 180or similar substrate. Disk 180 may be a magnetic disk for data storage(e.g., for use in a hard disk drive) or alternatively, disk 180 may bean optical-type disk. Apparatus 100 has top die 130 and bottom die 135portions. Support portions 105, 110 and columns 115, 120 stabilize topdie portion 130 and bottom die portion 135.

Top die 130 includes air-bearing mandrel 140 disposed near a middleportion of top die 130, and has a tapered nose oriented to face bottomdie 135. Air-bearing mandrel is supported by air manifold 172 thatenables air-bearing mandrel passive axial movement. Air-bearing mandrel140 has a diameter sized to engage an ID 182 of disk 180. Top die 130also has first imprinting surface 160 disposed around air-bearingmandrel 140. In one embodiment, first imprinting surface 160 may beadjacent or coupled to first elastomer pad 161 to accommodate variationsin thickness of disk 180. First imprinting surface 160 may also be afoil having the track features to be pressed on a disk. In oneembodiment, first imprinting surface 160 has a circular shape to matchdisk 180. A centerline for air-bearing mandrel 140 is aligned with acenterline 192 for first imprinting surface 160.

Bottom die 135 has a circular cavity 165 to contain an elastomericannulus. Bottom die 135 also includes an annular air manifold 170disposed substantially within cavity 165 to position disk 180. In oneembodiment, disk 180 is positioned by floating disk 180 within cavity165. Bottom die 135 also has a cylindrical opening 150 sized to receivetapered nose 145 of air-bearing mandrel 140. Bottom die 135 has secondimprinting surface 162 adjacent to second elastomer pad 163, with acenterline 194 aligned with the centerline 192 of first imprintingsurface 160 of air-bearing mandrel 140. In one embodiment, the die bodyelements including air-bearing mandrel 140 are of circular configurationand like materials, thus minimizing thermal distortion and maintainingcritical clearances at the air-bearing surfaces. Examples of materialsthat may be used for the die body elements include, but are not limitedto tool steels such D2, M2, and 440-C.

In one embodiment of a method to align and imprint disk 180 withapparatus 100, disk 180 may first be placed over circular cavity 165(which may contain an elastomer and heating element) by any number ofautomated methods. For example, in one embodiment, a robot or a pick andplace (“P&P”) device places disk 180 in circular cavity 165. Annular airslot 170 disposed near ID 182 positions disk 180 by floating disk 180 afew thousands of an inch above lower die cavity 165. In an alternativeembodiment, a second imprinting surface 162 adjacent second elastomerpad 163 may be disposed on disk cavity 165 and oriented to face a bottomside of disk 180. Disk 180 is initially axially constrained by shallowOD cavity walls that are a few thousands of an inch greater than thenominal diameter of the disk 180.

Apparatus 100 closes by top die 130 descending axially towards lower die135. Upon die assembly 100 closure, tapered nose 145 of air-bearingmandrel 140 freely guides the floating disk ID 182 into coincidentalignment with the centerline 190 of the top die 130. Because theair-bearing mandrel 140 moves freely on its own axis via air-bearingsupport, with its own weight directing a small downward force,air-bearing mandrel 140 remains in controlling contact with disk 180 asthe centerline 190 of air-bearing mandrel 140 is aligned with thecenterline 196 of disk 180 (and vice versa). Very low volumes of cleandry air (“CDA”) may be necessary to support the disk 180 and air-bearingmandrel 140.

With the centerline 196 of disk 180 aligned with the centerline 192 ofair-bearing mandrel 140 and first imprinting surface 160, top die 130continues to descent towards lower die portion 135. Tapered nose 145 ofair-bearing mandrel 140 lowers toward bottom die 135, and firstimprinting surface 160 becomes in contact with the disk surface toimprint disk 180. Depending on whether an imprinting surface is disposedon top die 130, bottom die 135, or both (e.g., first and secondimprinting surfaces 160, 162), either one or both sides of disk 180 maybe imprinted. This method provides precise side-to-side alignment andrepeatability for the imprinting of disk 180. Apparatus 100 passivelyaligns disk 180 with imprinting surfaces eliminating the need forprecision actuators or similar machinery. As such, the use of apparatus100 provides greater reliability, reduced operating costs andmaintenance, improved accuracy and repeatability, and faster cycletimes. In one embodiment, apparatus 100 attains a disk-to-die alignmentof +/−5 microns or better.

FIG. 2 illustrates a cross-sectional view of another embodiment of adisk alignment apparatus 200 for patterned media production. Apparatus200 passively aligns and imprints a substrate (e.g., a disk). Apparatus200 has top die 230 and bottom die 235 portions. Top die 230 includesfirst air-bearing mandrel 240 disposed near a middle portion of top die230, and has a first tapered nose 242 oriented to face bottom die 235.First air-bearing mandrel 240 has a diameter sized to engage an ID 282of disk 280. Top die 230 also has a first imprinting surface 260disposed around first air-bearing mandrel 240. In one embodiment, firstimprinting surface 260 may include an elastomer pad to accommodatesurface variations of disk 580 or imprinting surface 260 (e.g., animprinting foil). In one embodiment, first imprinting surface 260 has acircular shape to match disk. A centerline 290 for first air-bearingmandrel 240 is aligned with a centerline 292 of first imprinting surface260. Support portions 205, 210 stabilize top die portion 230 and bottomdie portion 235.

Bottom die portion 235 has second air-bearing mandrel 245 disposed neara middle portion, with a second tapered nose 244 oriented to firsttapered nose 242 of first air-bearing mandrel 240. As with first taperednose 242 of first air-bearing mandrel 240, second tapered nose 244 ofsecond air-bearing mandrel 245 is also sized to engage an ID 282 of disk280. In one embodiment, bottom die 235 may also have a second imprintingsurface 262 disposed around second air-bearing mandrel 245. A centerline294 for second air-bearing mandrel 245 is aligned with a centerline 296of second imprinting surface 262. In one embodiment, bottom die portion235 of apparatus 200 rests in a dual air-bearing nest, with one planarsurface 276 and one spherical surface 278. The dual air-bearing nest ofplanar surface 276 and spherical surface 278 allows spherical seat 250of bottom die portion 235 freedom of motion to rotate about atheoretical center 298 of the top surface of disk 280.

In one embodiment of a method to align and imprint disk 280 withapparatus 200, disk 280 may first be placed on bottom die portion 235(e.g., by robot or P&P device) such that second tapered nose 244 ofsecond air-bearing mandrel 245 engages an ID 282 of disk 280.Specifically, disk 280 is placed on the lower mandrel 245 and is securedseveral thousandths of an inch above second imprinting surface 262within a cavity 265 of bottom die portion 235. The cavity 265 is sizedslightly larger than disk 280 to contain disk 280 within bottom dieportion 235.

Disk 280 is initially axially located by the first tapered nose and thenby the second tapered nose 244 of second air-bearing mandrel 245 ofbottom die portion 235. As discussed above, a duplicate precisionair-bearing linear mandrel (e.g., first air-bearing mandrel 240) residesin top die portion 230. Upon closure of top and bottom die portions 230,235, the noses 242, 244 of first and second air-bearing mandrels 240,245 have three finger-like configurations with tapered faces which allowthem to mesh, capturing disk 280 on both ID chamfers. Thus, the bottomdie portion 235 aligns to top die portion 230 using centered disk 280 asthe connecting medium. First air-bearing mandrel 240 of top die portion230 is urged downward by its own weight (and air pressure if needed),and second air-bearing mandrel 245 of bottom die portion 235 is urgedupward via a small differential air pressure. Bottom die portion 235freely floats on a flat air-bearing plane 276 into alignment with thecenterline 290 of top die portion 230. Plane matching of firstimprinting surface 260 and second imprinting surface 262 is attained bythe passive movement of the spherical air bearing surface 278 ofspherical seat 250. Surface 278 has its radius of curvature focused atthe center point of the top surface of the disk 280 to minimize relativemotion between disk 280 and second imprinting surface 262. In oneembodiment, excess freedom of motion of spherical seat 250 may becontrolled by cleats. Very low volumes of CDA may be used to supportair-bearing mandrels 240, 245. As such, apparatus 200, by utilizing afull-floating, multi-axis lower die portion and air-bearing mandrels,achieves auto-alignment of both sides of a disk to imprinting surfaces.If die sets 205, 210 are very precise, the spherical alignment featuremay be removed and the planar system retained to achieve coaxialalignment of 205, 210.

FIG. 3 illustrates a cross-sectional view of another embodiment of adisk alignment apparatus for patterned media production. Apparatus 300has top die portion 330 and bottom die portion 335 that establishes afundamental side-to-side alignment and repeatability of patterned media(e.g., a disk). Bottom die portion 335 has air-bearing supportedalignment mandrel 340 disposed near a center portion, with a taperednose 342 extending towards top die portion 330. Support portions 305,310 and columns 315, 320 stabilize top die portion 330 and bottom dieportion 335.

Tapered nose 342 of air-bearing mandrel 340 is sized to engage an ID 382of disk 380. As described in greater detail below with respect to FIGS.7A and 7B, imprinting surfaces 360, 362 may be hermetically sealed overtop and bottom portions 330, 335 to form shallow cavities 350, 351, 352,353. Top and bottom die portions 330, 335 also have pressurized fluidoutlets 370, 372, 374, 376 in fluid communication with the hermeticallysealed shallow cavities 350, 351, 352, 353 for the delivery and removalof fluids (e.g., liquid or gas) used to press imprinting surfaces 360,362 on disk 380. In one embodiment, apparatus 300 may have a total offour pressurized fluid outlets, although more or less than four may beutilized. A centerline 390 for air-bearing mandrel 340 of bottom dieportion 335 is aligned with imprinting surfaces 360, 362 disposed on topand bottom die portions 330, 335. Bottom die portion 335 also has spring345 to allow mandrel 340 axial movement. All of the die parts may be ofcircular configuration and like materials, thereby minimizing thermaldistortion and maintaining critical clearances at the air-bearingsurfaces.

In one embodiment, imprinting surfaces 360, 362 are made of compliantmaterial to allow for flexibility when making contact with a disksubstrate (e.g., disk 380). The disk substrate may possess inherentvariations in thickness which would require that imprinting surfaces360, 362 be flexible to conform to the variations. FIG. 7A illustrates across-sectional view of one embodiment of imprinting surfaces 710, 712hermetically sealed over die portions 720, 722 to form hermeticallysealed cavities 730, 732. For clarity of explanation, the entire diskalignment apparatus is not shown. Imprinting surfaces 710, 712 may besealed to die portions 720, 722 by welding (e.g., laser or braze),soldering, or electric arc welding. By welding imprinting surfaces 710,712 to die portions 720, 722, leakage of fluid passed through cavities730, 732 may be prevented during the imprinting process. FIG. 7Billustrates a cross sectional view of an alternative embodiment ofhermetically sealing imprinting surface 710, 712 over die portions 720,722. In this embodiment, o-rings 740, 742 may be used to seal imprintingsurfaces 710, 712 over die portions 720, 722. A slight vacuum at diecavities 730, 732 may hold imprinting surfaces 710, 712 in place untilclamping action of die closure is established. Alternatively,elastomeric materials (e.g., rubber and other comparable polymers) andmetals (e.g., for use with ultra high vacuum seals) may be used in placeof o-rings.

It may be appreciated by one skilled in the art that a pre-formed cavityadjacent to an imprinting surface may not be necessary for theapplication of localized heating and cooling elements. In oneembodiment, a mechanical piston may be disposed adjacent to theimprinting surface to force contact with a disk substrate.Alternatively, the application of a heating or cooling element to theimprinting surface may cause a cavity to form as the imprinting surfaceflexes to make contact with the disk substrate.

Referring again to FIG. 3, in one embodiment of a method to align andimprint a disk 380 with apparatus 300, disk 380 is placed on air-bearingmandrel 340 of bottom die portion 335 (e.g., by a robot or P&P device).Upon placement, disk 380 residing several thousandths of an inch aboveimprinting surface 362 of the lower die cavity 352. As top die portion330 closes over bottom die portion 335, disk 380 locks in place with ID382 of disk 380 engaging the tapered nose portion 342 of air-bearingmandrel 340. Upon closure of top and bottom die portions 330, 335 acenterline 396 of disk 380 is aligned with the centerlines 390, 392 oftop and bottom die portions. Next, the cavities 350, 352 underlyingimprinting surfaces 360, 362 are charged with high-pressure fluid (e.g.,a gas or liquid) forcing the features of the imprinting surfaces intothe polymer coating of disk. Fluid is delivered through pressurizedfluid outlets 370, 372, 374, 376. Examples of fluids that may be usedinclude, but are not limited to high-pressure gas (nitrogen), hydraulicoil, and thermal working fluids such as Dow Therm™ or Marlotherm N™. Tocomplete the imprinting process, pressure is reduced to zero and thefluid is allowed to flow through the cavities followed by cooling fluidto carry off residual heat and cool the impressed surface of disk 380.Cooling the disk and imprinting surface may facilitate the separation ofthe disk from the imprinting surface.

The coating of a disk substrate may be an integral part of a patternedsubstrate or removed after suitable development. By imprinting featuresin a coating via a stamper, it may be used as a stencil to enablepatterning of the substrate surface by subsequent material additive orsubtractive processes (e.g., plating through a mask or etching through amask), and can often be facilitated if the imprinting is performed at anelevated substrate temperature. In the latter case the resultant maskwould be removed after performing the additive or subtractive steps.Higher temperature can soften the material to be imprinted and therebyimprove embossed feature fidelity and increase stamper life. Moreover,separation of the stamper from the imprinted surface may be facilitatedby cooling the substrate below the imprinting temperature. Hence, it maybe desirable to equip the press with elements to heat and cool the disksubstrate prior to and after imprinting it via the stamper. Provision ofsuch cooling and heating elements is preferably accomplished by placingsuch elements in close proximity to the back of each stamper. Localizedheating and cooling of the disk substrate may not be necessary in orderachieve successful stamping. The entire disk alignment apparatus (e.g.,apparatus 300) may be subjected to heating and cooling elements to stampa disk substrate.

As explained above, one method of heating and cooling may include usinghot and cool fluids in the cavities behind the imprinting surfaces(e.g., imprinting surfaces 360, 362), membranes, or foils.Alternatively, annular blocks may be disposed in close proximity to theimprinting surfaces. These blocks may contain embedded electric heatingcoils or thermoelectric cooling devices. In another embodiment, annularquartz heating lamps or resistive ribbons adhered disposed near theimprinting surface may be used in combination with cooling fluids.

FIG. 8 illustrates one embodiment of a heating and cooling device forimprinting a disk. The device includes a thermodynamic press 800 havingpressurized fluid sources in communication with fluid outlets (e.g.,370, 372, 374, 376 of FIG. 3) of a disk alignment system for thedelivery of heating and cooling elements for imprinting a disksubstrate. For clarity of explanation, a partial cross-sectional view ofdisk substrate 810 is shown, with imprinting surface 820 disposedadjacent to disk substrate 810. A hermetically sealed cavity 830 isdisposed adjacent to imprinting surface 820. Cavity 830 also has port860 in fluid communication with heating element 840 and port 862 influid communication with heat exchanger 870.

In operation, heating coils 842 heats a fluid 844 (e.g., a liquid orgas) contained in heating element 840 to a working temperature. Piston805 of heating element 840 displaces hot, working fluid 844 from heatingelement 840 through port 860 and into cavity 830. Working fluid exitscavity 830 through port 862 displacing an inert gas (e.g., Nitrogen)towards heat exchanger 870. Check valves 880, 882 may be activated tostop a free-flow of working fluid 844 and allow piston 805 to achieve apre-selected force to compress imprinting surface 820 against disksubstrate 810 by transferring the heat of working fluid 844. Piston 805may then be retracted, lowering a system pressure, and withdrawing hotworking fluid 844 through fluid return line 890. Chilled gas from heatexchanger 870 follows and replaces the exiting hot fluid from cavity 830and cools imprinting surface 820.

FIG. 4 illustrates a perspective view of another embodiment of a diskalignment apparatus 400 for patterned media production. Apparatus 400aligns and imprints a substrate (e.g., a disk). Apparatus 400 has topdie portion 430 and bottom die portion 435 that establishes fundamentalrepeatability of the patterned media (e.g., a disk). Support portions405, 410 and columns 412, 414, 416 (a fourth column is not shown in thisview) stabilize top die portion 430 and bottom die portion 435. Bottomdie portion 435 has air-bearing supported alignment mandrel (not shown)disposed near a center portion, with a tapered nose 445 extendingtowards top die portion 430. Tapered nose 445 of air-bearing mandrel issized to engage an ID 482 of disk 480. Top and bottom portions 430, 435also have first and second imprinting surfaces. In this view, onlysecond, imprinting surface 462 is shown.

In one embodiment, first and second imprinting surfaces 460, 462 areheld in place by pico-actuators 470, 472, which control side-to-sidemovement of first and second imprinting surfaces 460, 462. Top andbottom die portions 430, 435 also have pressurized fluid outlets 450,452 for the delivery and removal of fluids used to charge annularpistons (not shown), thus press imprinting surfaces on disk 480. Acenterline 490 for air-bearing mandrel 440 of bottom die portion 435 isaligned with imprinting surfaces 460, 462 disposed on top and bottom dieportions 430, 435. All of the die body elements and air-bearing mandrel440 are of circular configuration and like materials, thus minimizingthermal distortion and maintaining critical clearances at theair-bearing surfaces.

In one embodiment of a method to align and imprint a disk 480 withapparatus 400, disk 480 is placed on the tapered nose portion 445 ofmandrel 440 (e.g., by a robot or P&P device), residing severalthousandths of an inch above second imprinting surface 462 of lower dieportion 435. Top die portion 430 is closed over disk 480 and locked inplace against imprinting surfaces 460, 462. Upon closure of top andbottom die portions 430, 435, a centerline of disk 480 is aligned withthe centerlines of top and bottom die portions 430, 435 (centerlines arenot shown in this perspective view of apparatus 400). The cavities (notshown) underlying the imprinting surfaces 460, 462 are then charged withhigh-pressure gas forcing the imprint features into the polymer coating.Fluid is delivered through pressurized fluid outlets 450, 452. Tocomplete the imprinting process, pressure is reduced to zero and apurging gas flows through the cavities to carry off residual heat andchill the impressed surfaces of disk 480. In an alternative method, acharge of combustible gas, such as hydrogen and oxygen, may be used tocreate heat and percussive pressure to emboss the imprinting surfacesinto the polymer layer of disk 480. Subsequent purging of the cavitiescools the foil and polymer.

FIG. 5 illustrates, in flowchart form, one method for passively aligninga disk for patterned media production. The method starts at block 510 byproviding a die set having an upper portion and a lower portion, with asurface of the imprinting surface or foil disposed on the lower portionand facing the upper portion. Next, at block 520, a disk floats abovethe imprinting surface within a cavity of the lower portion. At block530, an ID of the disk engages a tapered nose portion of an air-bearingmandrel coupled to the upper portion of the die set. At block 540, topdie portion closes over the lower portion, such that tapered noseportion of the air-bearing mandrel guides the floating disk ID intocoincident alignment with a centerline of the air-bearing mandrel andthe imprinting surface.

FIG. 6 illustrates, in flowchart form, another method for passivelyaligning a disk for patterned media production. The method starts atblock 610 by providing a die set having an upper portion and a lowerportion, with a surface of an imprinting foil disposed on the lowerportion and facing the upper portion. At block 620, a disk positionedabove the imprinting foil within a cavity of the lower portion. At block630, an ID of the disk engages a first tapered nose portion of a firstair-bearing mandrel coupled to the upper portion of the die set. Atblock 640, a second tapered nose portion of a second air-bearingmandrel, coupled to the upper portion of the die set, intermeshes withthe first tapered nose portion. Upon closure of top and bottom portions,the first and second tapered nose portions guides the lower die via thedisk ID into coincident alignment with a centerline of the fist andsecond air-bearing mandrels and the imprinting foils.

In the foregoing specification, the invention has been described withreference to specific exemplary embodiments thereof. It will, however,be evident that various modifications and changes may be made theretowithout departing from the broader spirit and scope of the invention asset forth in the appended claims. The specification and figures are,accordingly, to be regarded in an illustrative rather than a restrictivesense.

1. A method, comprising: passively aligning an imprinting surface with adisk; and imprinting the disk with the imprinting surface, wherein afirst air-bearing mandrel freely guides a first centerline of the diskinto coincident alignment with a second centerline of the imprintingsurface.
 2. The method of claim 1, wherein passively aligning furthercomprises: providing a die set having an upper portion and a lowerportion, with the imprinting surface disposed on the lower portion andfacing the upper portion; positioning the disk, above the imprintingsurface, adjacent a cavity of the lower portion; engaging an ID of thedisk with a tapered nose portion of the air-bearing mandrel coupled tothe upper portion of the die set; and closing the top portion over thelower portion.
 3. The method of claim 2, further comprising adjusting ahorizontal position of the imprinting surface with a plurality ofpico-actuators coupled to the imprinting surface.
 4. The method of claim1, wherein imprinting comprises charging the imprinting surface with aheating element to force the imprinting surface on the disk.
 5. Themethod of claim 4, wherein the heating element comprises a hot fluid. 6.The method of claim 1, wherein imprinting comprises cooling the diskwith a fluid.
 7. The method of claim 6, wherein the fluid comprises agas.
 8. The method of claim 6, wherein the fluid comprises a liquid. 9.The method of claim 1, wherein passively aligning further comprises:providing a die set having an upper portion and a lower portion, withthe imprinting surface disposed on the lower portion and facing theupper portion; positioning the disk, above the imprinting surface,within a cavity of the lower portion; engaging an ID of the disk with afirst tapered nose portion of the first air-bearing mandrel coupled tothe lower portion of the die set; and intermeshing a second tapered noseportion of a second air-bearing mandrel, coupled to the upper portion ofthe die set, to close the top portion over the lower portion, wherein,upon die closure, the first and second tapered nose portions guide thedisk ID into coincident alignment with a centerline of the first andsecond air-bearing mandrels and the imprinting surface.
 10. The methodof claim 9, wherein providing a die set further comprises the lowerportion of the die set having a dual air-bearing nest of a planarsurface and a spherical surface to enable the bottom die portion torotate about a center of the disk.
 11. The method of claim 9, furthercomprising adjusting a horizontal position of the imprinting surfacewith a plurality of pico-actuators coupled to the imprinting surface.12. The method of claim 9, wherein imprinting comprises charging theimprinting surface with a heating element to force the imprintingsurface on the disk.
 13. The method of claim 12, wherein the heatingelement comprises a gas.
 14. The method of claim 12, wherein the heatingelement comprises a liquid.
 15. The method of claim 9, furthercomprising cooling the disk with a fluid.
 16. The method of claim 15,wherein the fluid comprises a gas.
 17. The method of claim 15, whereinthe fluid comprises a liquid.